From 2cb39a4ff1ae6396914a2d42c50f0dbf0ab0ce10 Mon Sep 17 00:00:00 2001
From: Nero <41307858+nero@users.noreply.github.com>
Date: Fri, 8 May 2020 20:48:23 +0000
Subject: [PATCH] Implement lba read

---
 kernel/diskio.asm | 56 +++++++++++++++++++++++++++++++++--------------
 1 file changed, 40 insertions(+), 16 deletions(-)

diff --git a/kernel/diskio.asm b/kernel/diskio.asm
index 1ff7504..3f344a4 100644
--- a/kernel/diskio.asm
+++ b/kernel/diskio.asm
@@ -9,27 +9,28 @@ disk_current:
 lba_supported:
 	resb 1
 
+	; Seek state and geometry info for CHS access
 disk_chs: ; DL, DH, CL, CH for int 13h CHS functions
 	resb 4
-disk_dap: ; disk access packet for int 13h EBIOS functions
-	resb 0x10
-
 disk_spc: ; sectors per cylinder = heads * spt
 	resw 1
 disk_spt:
 	resb 1
 
+	; Partition conf from MBR or dummy for floppies
 part_offset:
 	resd 1
 part_size:
 	resd 1
 
-	; Disk access packet for EBIOS extensions
-dapps:	equ 0 ; byte packet size
-dapnum: equ 2 ; word number of sectors to transfer
-dapbuf: equ 4 ; dword transfer buffer
-dapsec:	equ 8 ; qword absolute sector number
-dapsiz:	equ 16
+dap:	; Disk access packet for EBIOS extensions
+	resw 1
+dap_sectors:
+	resw 1
+dap_buffer:
+	resd 1
+dap_sector:
+	resq 1
 
 	section .text
 
@@ -46,14 +47,15 @@ dncl:	rcl dl, 1
 	ret
 
 	; Select a drive for I/O
+	; This leave the first sector of the partition in the buffer
 	; IN	dl	0=A, 1=B, 2=C, 3=D
 select:	mov byte [disk_current], 0xFF
 	mov byte [lba_supported], 0
-	cmp dl, 0x02
-	jc select_floppy
-	; detect EBIOS/LBA extensions
 	call dnconv
 	mov byte [disk_chs], dl
+	cmp dl, 0x80
+	jc select_floppy
+	; detect EBIOS/LBA extensions
 	mov ah, 0x41
 	mov bx, 0x55AA
 	int 0x13
@@ -123,6 +125,9 @@ seek:	push ax
 	pop ax
 	jz seek_zero
 
+	test byte [lba_supported], 1
+	jnz seek_lba
+
 	; dx:ax = lba
 	div word [disk_spc]
 	xchg ax, dx
@@ -147,14 +152,26 @@ seek_zero:
 	mov byte [disk_chs+1], 0
 	mov word [disk_chs+2], 1
 	; set lba data to first sector
-	lea di, [disk_dap+dapsec]
-	mov cx, 4
 	xor ax, ax
-	rep stosw
+	xor dx, dx
+seek_lba:
+	mov word [dap], 0x10
+	mov word [dap_sectors], 1
+	mov word [dap_buffer], disk_buffer
+	mov [dap_buffer+2], cs
+	lea di, [dap_sector]
+	stosw
+	mov ax, dx
+	stosw
+	xor ax, ax
+	stosw
+	stosw
 	ret
 
 	; Read a sector into buffer
-read:	mov ax, 0x0201
+read:	test byte [lba_supported], 1
+	jnz read_lba
+	mov ax, 0x0201
 	mov dx, [disk_chs]
 	mov cx, [disk_chs+2]
 	lea bx, [disk_buffer]
@@ -163,6 +180,13 @@ read:	mov ax, 0x0201
 	int 0x13
 	ret
 
+read_lba:
+	mov ah, 0x42
+	mov dl, [disk_chs]
+	lea si, [dap]
+	int 0x13
+	ret
+
 	; Write a sector into buffer
 write:	stc
 	ret